Space charge reaction device



A g- 1952 H. M. WAGNER SPACE CHARGE REACTION DEVICE Filed Jan. 25, 1951 DISTANCE POTENTIAL FIG.3

FIG.2

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IN V EN TOR. HERBERT M. WAGNER Patented Aug. 19, 1952 UNITED STATES TENT -oFF1;c-E

SPACE CHARGE REACTION DEVICE Herber-t ,M. Wagner, Asbury Park, N. J assignor to the United States of America as represented by the Secretary of the Army tron. tubes of av typeWherein one electron stream is employdto control the flow of electrons in another electronstream. Particularly, the invention. relates to a spacei charge reaction type of'electron tubeawherein 'an electron stream or small'current isemployed to control an electron stream of greater current.-

A variety of vacuum' tube. arrangements have previously been proposedwherein two electron streams have been arranged to interact so that changes in one of the streams produce larger corresponding changes in the other electron stream. Most-oi these proposed devices, While producing some measure of control, have generally been ineffective to control a stream carrying relatively large currents. A purpose of these attempts to control one electron stream by another'electron. stream is to avoid the use of a control or grid electrode so that the detrimentalcapacitive and inductive effects of the-physical control element may be avoided. However, "so far as is known, these attempts have for one reason oranother proved of little value, particularly in producing a control of relatively large currents, which is the particular case where the reactanceeffects of physical grid elements are detrimental.

It'is', accordingly, an object of the present inventidn to provide an electron relay of improved fori'ii Wherei'nafirst electron stream is controlled by a second electronstream which avoids some of the disadvantages and limitations of prior art proposals;

- Itisalso an object of the presentinvention to provide aspacecharge'reaction tube wherein an electron streafn of small current density is utilized to control'a second electron stream of larger current density.

In' accordance" with the present invention, a space charge reaction device is comprised of means for producing a first electron stream having a' predetermined velocity characteristic, which characteristic comprises a region of normally'constant velocity. Means are also provided for controlling the velocity of thestrea'm in the mentioned region comprising a second electron stream traversing the region at a velocity of the sameforder as the aforementioned constant. ve locity. and in a direction. substantially orthogonal amended'April 30, 1928; 370 0. G. 757) 2 to the direction of the first electron stream. Means are also provided for varying thejdensity of the second electron stream to produce corresponding variations in-the first electron stream. For a .better understanding of the invention, together with other and further objects thereof, reference is had to the following description taken in connection .with the accompanying drawingand itsscope will be pointed'out in the appended claims.

In the drawing: Figs. 1 and .4are schematicdrawings of aspace charge reaction tube andassociated circuit elements arrangedfor, operation in accordance with the present invention; Fig. 2 is a'diagra'mshowingthe potential'gradient between. electrodes in the Fig. 1 embodiment of theinvention foruse in describing the operation; Fig. 3 .represents an alternative structural arrangement of Fig. 1 and Fig. 5 represents an alternative structural'arrangement of Fig. 4.

Referring now moreparticularly to the drawing, in Fig. 1 there is shown a space charge reaction electron tube in, accordance with a'preferred form of the invention Twherein'the-tube is comprised of an evacuated envelope I0 containing a source of electrons, comprising aheater element [4, cathode, l5, control grid l6 and accelerating electrode I! to provide a source of electrons of predetermined :velocity which traverse the tube and normally strike the collector electrode I8. The electrons from cathode? f4 pass substantially in a direction orthogonal to another electron .stream which is of larger "total current and is provided by cathode 20 activated by heater l9. Acceleratingelectrodes 2i and22 serve to produce a predeterminedwelocity characteristic for this electron stream inits traversal of the space to collector 23; Theielect'rod'e 22 located in front of collector 23 is maintained at a potential which is generally the same as, or difiers only slightly from, the'potential of electrode 2|. The space'be tween electrodes 2! and 22 may be referred to asa region 16f depressed potential or a region of space charge; sometimes referred to as a virtual cathode. Operating potentials are provided by battery I3 and the connections therefrom to the several electrodes. Input signals are applied atterminals ll between cathode l5,and control electrode l6 andbattery 24 serves to provide suitable biaspotential to the control grid. It. An output ,load for the tube is indicated by resistor iii coupled between the anode-electrode 23 and thepositive terminal of 3 battery |3 and output terminals, labeled l2, are provided.

Considering now the operation of the system and referring also to Fig. 2, the potential gradient in a plane section between cathode 20 and electrode 23 is indicated for a condition corresponding to the absence of current flow by the solid line graph A, B, C, D. In this, graph distances corresponding to the spacing of the electrode elements are indicated by similar reference numerals. The solid line graph,-therefore,;represents the potential gradient between the tube elements 20, 2|, 22 and 23 when unaffected by'the presence of an electron stream and it is evident.

from the graph that between electrodes 2|and trons passing through the perforations of accelerator 2| proceed to the perforations of electrode 22 at substantially constant velocity. H

Consider now the effect of the electron stream originating at cathode -|5 (hereafterto' be referred to as the second electron stream) and traversing the space between acceleratoi" and collector l3 in a direction substantially orthogonal to an electron stream (hereafter to be referred to as the first electron stream) traversing the space between electrodes 2| and 22. It will be noted that the electrodes 20, 2|, 22 and 23 associated with the first electron stream are much larger physically than the electrodes associated with the second controlling stream and that the distance between electrodes IT and I8 is relatively long. It will also be noted that the potential between cathode|5 and collector 18, as indicated by the tapped positions on battery I3, is somewhat higher than the potential difference between cathode 2Uand electrode 2 I, so that the second or controlling electron stream proceeds between electrodes l1 and It at a velocity of the same order and preferably slightly higher than the normally constant Velocity 'of electrons between electrodes 2| and 22. Because of the relatively long path from ||to '|8 and the comparable velocity of the streams, the electrons of the controlling second stream remain within the space charged region of the controlled first stream a relatively long time. 'With a chosen initial setting of bias battery 24, the efi'ect of the controlling electron stream upon the first electron stream is to providea new curve for the potential gradient betweenelectro'des 2| and 22, as indicated by the long dashed line curve between the points A and B in Fig. 2. This curve represents a setting of the bias on grid: I6 for proper operation of the device. It will be clear that if control grid |6 is'made more negative, the operating gradient of the tube may reach the limit indicated by the short dashed line be tween points B and cor Fig. 2.' In operation, then, with a signal voltage applied between cathode |5 and'control grid Hi, the curve of potential varies between the short dashed line curve and the solid line curve with the long dashed line curve indicating a center value of operation.

The velocity of the electrons traversing the space between electrodes 2| and 22 will, of course, vary as the square root of the potential in this region. It will be clear, therefore, that varying the density of the electrons in the controlling electron stream operates to produce corresponding variations in the velocity. of the controlled electron stream. It follows, therefore, that a signal applied to the input terminals I produces a corresponding variation in the velocity of the controlled electron stream. This variation in velocity in accordance with the input signal results in a so-called bunching of the electrons, so that, in effect, the electrons in the controlled stream are modulated in accordance with the applied signal and since this is a stream of greater current, an amplified signal is produced across the output impedance 25.

The arrangement in Fig. 1 has implied that planar electrodes will be employed. It is evident, of course, that other forms of the device might be more economical of space and have constructional advantages'and Fig. 3 illustrates by a cross section diagram one cylindrical form which the tube may take. Here, and throughout the specification, similar reference numerals are employed to indicate similar elements. Thus, in Fig. 3, the envelope lfl'has located within it and arranged in concentric fashion, the cylindrical electrodes 20, 2|, 22 and 23, which provide the first electron stream and within the space between electrodes 20 and 2| the cathode l5, control grid l6 and accelerating electrode I! are located on one side of cathode 20 and collector |8 is located on the opposite side of cathode 2|]. The lines having arrowheads indicate that the electrons from caths ode I5 travel in circular paths from each face of cathode IE to collector'l8 and generally, due to the operating potential chosen for collector 18, these electrons constituting the second: electron stream will traverse the region'between electrodes 2| and 22 in a direction substantially-onthogonal to the direction of the radial flow of electrons in the first electron stream. An alternative arrangement for providing a cylindrical tube structure wherein the second electron stream is orthogonal to the first electron stream would be an arrangement similar to that shown in Fig. 5, and which will be more fully explained with reference to the embodiment'shown in Fig. 4, and presently to be described.

Referring now particularly to Fig. '4, the arrangement there shownis comprised of the same elements as shown in Fig. 1, except that the two electrodes 2| and 22 associated with the first electron stream and the accelerating electrode ll of the second electron stream have been omitted, and in place thereof a focusing coil 2'5 is provided which is energized from a direct current source, not shown, to provide a magnetic field which is coaxial with the normal direction of the second electron stream between cathode l5 and collector I8. As is well known, the coaxial magnetic field will cause a rotation of the electrons in the second electron stream such thatthe stream converges to impinge on collector l8, while impingement of these electrons on electrode 23 is reduced or avoided. In effect, the magnetic field is equivalent in its end result to the electrodes 2| and 22 as employed in Fig. 1, so that the second electron stream traverses a space charge region between cathode 20 and electrode 23 to control the velocity of the electrons in this space. Accordingly, as in the Fig. 1 arrangement, an input signal applied at terminals operates to control the velocity and, accordingly, to provide corresponding variations in the density of a larger electron current flowing between electrodes 2|] and 23. 4

It will be noted that in the described opera-- tion of both the Fig. 4 and Fig. 1 arrangements of the present invention the second or control-- ling electron stream has a lower current and a velocity of the same order or preferably slightly higher than the velocity of the first electron ing is greater where the second electronstream enters, than where it leaves this region to impinge upon collector It. This variation of the spacing, as shown, causes the control effect of the secondelectron stream at the entering region of this space to be delayed relative to its effect at the exit part of the region. Compensation by varying the transit timefor the first electron stream is therefore accomplished progressively along the path in the direction of flow of the: second electron stream. v

, Fig. 5 illustrates a cylindrical form of the'Fig. 4 arrangement, wherein the cathode 2i! and anode 23 have concentric cylindrical form and arrangement, while the electrodes I5, l6 and collector [8 associated with the second electron stream are shown as planar elements to provide for the second electron stream a relatively long path in traversing the region between electrodes 20 and 23 in a direction orthogonal to the electrons of the first stream. The second electron stream for one particular group of electrons is indicated in dotted line 21 to show the rotation of the stream due to the magnetic field as it progresses through the space charge region. The rotation may be in small spirals as indicated, or the magnitude of the magnetic field may be adjusted so that the electrons in the second electron stream rotate or gyrate completely around the cathode 20 as they progress through the space charge region to collector Hi.

In each of the embodiments shown in Figs. 1, 3, 4 and 5, the arrangements provide means for producing a, first electron stream between electrodes 20 and 23 which has a predetermined velocity characteristic comprising a region of normally constant velocity and the electrodes l5, l6 and I8 and their orientation are such as to provide means for controlling the velocity of the first electron stream in the region of normally constant velocity which comprises a second electron stream traversing the region between the electrodes 20 and 23 at a velocity of the same order as the aforementioned constant velocity and in a direction substantially orthogonal to the direction of the first electron stream. The grid [6 provides means for varying the density of the second electron stream to produce corresponding variations in the velocity and density of said first electron stream.

It will be clear that a primary effect of the second electron stream upon the first stream is a control of velocity which results in so-called bunching of the electrons in their traversal of the region between electrode 2| and anode 23. Accordingly, it is preferable to space the anode 23 a suitable distance from electrode 22 to permit adequate electron drift so that the punching process is completed. In addition to the bunching produced by control of the velocity of the first electron stream, there is also density control by the second electron stream acting in efiect as an electron control grid to turn back a portion of..-i e..e ct 2n ;theifir t lectron-stream .5

h t the e nl cnt o spe u a a qemg is bunching by drift of the electrons neednotbe ent re y-re edup h The rode assoc ated n ththe rs eleetmn s m ha e n-i most d .n esi'ih a lane or c ved su ac :-.l -;w 4 evident to thosetskilled; in the artthat e ypev electrod mar zemnlqye i ine t w r jope at n n a hos n na r wa et f equenc es i o em ated F r; exa p the anodes? ma b in he t rm of a r eme ta it n F s. lan 4. mm formpinev en e wou r..e amp e. a i elqnsat tu e wa ui se t n h vin inane-para l yit -t zeir ttiq of, flow f the s c n lectr n t anindha in a longitudinal slot racin fiethode zdwherebydhe electrons of the first streammay'pass into the cavity. A cavity output coupling; circu V weal then be provided in known manner. 1 1.

While there has been-described what are'at present consideredto be .the f preferred embodiments of this invention, it willbe obvious to :those ski edin he a t t at var o s; ch ne si n o ficatio s m rbema e t e in wW hout.d nanti-11 from the invention, d. it i ...t ref e.eims l;i the appended claims 1 07993161 all. such; changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A space charge reaction device comprising means for producing a first electron stream extending a predetermined distance in a direction orthogonal to the direction of flow of said stream, said stream having a predetermined velocity characteristic comprising a region of normally constant velocity, means for controlling the velocity of said stream in said region comprising a second electron stream traversing said region at a velocity of the same order as said constant velocity and in said direction orthogonal to the direction of said first electron stream, said predetermined distance being chosen to provide a relatively long transit time for electrons of said second stream, and means for varying the density of said second electron stream to produce corresponding variations in the velocity and density of said first electron stream.

2. A space charge reaction device comprising means for producing a first electron steam extending a predetermined distance in a direction orthogonal to the direction of flow of said stream, said stream having a predetermined velocity characteristic comprising a region of normally constant velocity, means for controlling the velocity of said stream in said region comprising a second electron stream traversing said region at a velocity of the same order as said constant velocity and in said direction orthogonal to the direction of said first electron stream, said predetermined distance being chosen to provide a relatively long transit time for electrons of said second stream, means for modifying the transit time of the electrons in said first electron stream progressively along said predetermined distance to compensate for the said relatively long transit time for electrons of said second stream, and means for varying the density of said second electron stream to produce corresponding variations in the velocity and. density of said first electron stream.

3. A space charge reaction device in accordance with claim 2 wherein said modifying means comprises cathode and anode electrodes associated with said first electron stream and positioned to have progressively decreased spacing therebetween in the direction of flow oi said'second electron stream. a

i. Aspace charge reaction device'comp'rising a plurality of concentrically positioned cylindrical electrodes 'for producing a first" electron stream extending in a predetermined circular direction orthogonal to the radial direction of flow of said stream, said stream having a predetermined' velocity' characteristic comprising a region of normally constant velocity, means for controlling the velocity of said stream in said regioncomprising a second electron stream traversing said region at a velocity of the same order as said constant velocity'and in said direction orthogonal tothe direction of said first electronstream, and means for varying the density of said second electron stream to producecorresponding variations in the velocity and density of said first electron stream.'

5. A space charge reaction device comprising means for producing a first electron stream extending a predetermined distance in a direction orthogonal to the direction of flow of said stream, said stream having a predetermined velocity characteristic comprising a region of normally constant velocity," means 'for controlling the REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PATENTS Number Name Date 2,245,627 Varian June 17, 1941 2,338,237 Fremlin Jan. 4, 1944 2,407,667 Kircher Sept. 17, 1946 2,457,980 De Forest Jan. 4, 1949 2,558,001

Ramo Q. June 26, 1951 

